bartlett



MoaeL-y 2 'Sheets'Sheet 1..

' J. E. T. BARTLETT.

PROPELLER WHEEL.

No.,384,498. Patented June 12, 1888.

IIVVEIVTOR, 4 6.; 630%;

N. PETERS, Pbohrliihognpher. Washington. 0.1:.

UNITED STATES PATENT QEEICE.

JOHN E. T. BARTLETT, OF NEvV YORK, N. Y.

PROPELLER-WHEEL.

SPECIFICATION forming part of Letters Patent No. 384,498, dated June 12,1888.

Application filed October 28, 1887. Serial No. 253,661. (Mocleh) To allwhom it may concern:

Be it known that I, J OHN E. T. BARTLETT, a citizen of the UnitedStates, residing at New York city, in the county of New York and Stateof New York, have invented a new and useful Form of Propeller-Wheel,fully described and represented in the following specification and theaccompanying drawings,forming a part of the same.

My invention relates to an improvement in the shape of thepropelling-surface of the blades of propeller-wheels used in propellingvessels through or on the water; and the ob jects of my improvement are,first, to control the flow of water driven astern by the propeller,giving it a direction parallel to the axis of the driving-shaft andopposite to the motion of the vessel; second, to prevent the water beingraised by the centrifugal force generated by the angular velocity of thepropeller; third, to gain length of blade with given diameter, andthereby decrease the frictional resistance to be overcome by the enginein rotating the propeller at a given angular velocity, this resistanceincreasing as the square of the distance from the axis of the propeller;and, fourth, to eliminate the local surface disturbance and currentscaused by the dispersion of the water in any other form ofpropeller-wheel, and as the flow of Water is parallel to thelongitudinal axis of the shaft the banks are not washed away nor thebottom scoured by this form of propeller in navigating narrow or shallowwater-ways, such as canals. Iattain these objects by constructing thepropelling-surface of the blades of the propeller,which may have as manyblades as the fancy of the designer may desire-usually from two tofour-of the form illustrated in the accompanying drawings, in which-Figure 1 is a plan or top View of the propeller, showing alongitudinalsection of the blade on the right and projected sections atthe diameter d d, d (2,, and the characterizing curve 2 0 2, forming theprincipal feature of my invention. Fig. 2 is a front elevation of thepropeller, looking aft. Fig. 3 is a cross-section through thepropeller-shaft and the blade of the common form of screw-propeller, theblade being of such a nature that if it were turned on its axis, havingat the same time a motion of translation equal to the desired .pitch,.atrue pitch-wheel having a helicoidal surface precisely analogous to theArchimedean screw would be generated. Fig. etis a similar sectionthrough that form of propeller commonly known as the centrifugalpropeller,

which is formed on an oblique generatrix.

Fig. 5 is a section of my improved form of propeller-blade, and showsthat aplane passed through the axis of the propeller-shaft willintersect the blade in a parabolic curve.

Similar symbols refer to similar parts throughout the specificationandaccompanying drawings.

The base-line of abscissae 1 O 1, for determi n i n g the curve 2 0 2,is assumed to pass through the center line, 3 8, of the shaft midway ofthe length of the propeller-hub 4 4. The ordinates h h h 71,. and so onfor as many ordinates equidistant from each other as may be neces saryto determine the curve to the required degree of accuracy, arecalculated, using the variable quantity d as one of the values in theformula, said variable quantity being equal to twice the distance of thepoint at which it may be desired to erect the ordinate from the axis ofthe propeller, using the parabolic formula in which formula h equals theordinate h-h,

hh, and so on for the different values of (i The curve 2 0 2,drawnthrough these points,is a parabola.

Referring to the drawings, if a plane be passed through the axis of theshaft of a propeller of my construction intersecting the driving-surfaceof either of its blades A A A A, then will the intersection of saidplane and drivingsurface of the blades form a parabolic curve, 2 O 2,and the driving-surface will be a parabolic surface generated by therevolution of a semi-parabola, 0 2, whose vertex is 0, around thelongitudinal axis 0 3, having at the same time a motion of translation,positive or negative, in the direction 0 3, equal to the required pitchof the propeller.

Referring to Fig. 5, it will be seen that the curve of the blade thereinshown is a parabola having its vertex situated at 0, its focus at F. Thefocal distance is represented by f. The lines 8 s indicate the flow ofwater to the wheel, partaking as it does of the contour of the run ofthe ship, as is actually the case in practice. After the particles ofwater have passed behind the blades, the directional force of the wheelwill drive it in one of two directions-viz., it will be reflectedparallel to the shaft-axis. Why! Because water beingincompressible itcannot be forced at F, and as the reflecting-surfilce must drive it oneway or the other it must follow the lines d (Z. The wheel, taking waterperpendicularly to its feedingedge, will draw from the larger areafacing the wheel, and said area being in the same ratio as the square ofthe length of the curved directrix is to the square of the actual radiusof the wheel, the diameter of the wheel being the smaller diameter of afrustum of a cone whose elements are parabolas, or what maybe called aconic paraboloid. The water behind the wheel will be compressed, or,more strictly speaking, the air in the water which flows to thepropeller is compressed, so that the wheel works in solid water, thuscorrecting any tend cncy to race, racing being a term used to representthe tendency of propeller-wheels to slip ahead of the water withvariable speed,0wing to the existence of air in the water; hence a wheelof my construction causes less vibration than the other forms, becauseit works on solid water.

The driving-surface of this design of propeller will act on the sameprinciple as sound and light reflectors constructed on the sameprinciple; hence the water driven astern must necessarily be driven in astream parallel to the longitudinal axis of the propeller -shaft. Anyparticle of fluid passing behind the leading edge A of thepropeller-blade will be forced back by the advancing surface of thepropeller, and the superposed particles being prevented following orflowing off the blades by the re fleeting-surface. Before said particlecan acquire centrifugal force from contact with a rotating surface ofhigh velocity it will have been left behind by the advancing propeller.Having no tendency to rise to the surface, it will be reflected parallelto the axis of the shaft, as the least resistance is in the direction ofthe wake of the vessel.

The increase in length of blades is clearly shown on the right-handblade, Fig. 1, and the length gained is the difference in length of thecurved line 0 2 and the straight line 0 1, the length of the curveextending to the point 71 a distance 71 -41 beyond the diameterof thepropeller, and as the frictional horse power required to rotate apropeller is equal to the surface-pressure multiplied by the square ofthe velocity the velocity will be greater as the diameter is increased.Therefore a wheel of the same blade area can be obtained with lessdiameter and equal length of blade in this construction, and willrequire less power to rotate it at a given angular velocity than astraight blade of equal length.

The propelling-surfaces of propellers of my peculiar constructionprevent the water flowing ofi radially or tangentially; hence there areno waves on the surface caused by the rotation of the propeller, and asthe water is but slightly agitated there is no tendency to wash awaybanks or scour the bottom of water-ways of small sectional area, and myexperiments have always shown a wake of aslittle commotion as is made bythe passage of a vessel under sail; hence I believe this design ofpropeller is particularly adapted to steam-navigation on canals.

I am aware that many designs of propellers have been rnade with curvedblades of different forms having names given them from some fanciedresemblance they may have to wings of birds and objects. I therefore donot claim curved blades as so constructed; but

XVhat I desire to claim is- The herein described propeller blades curvedin the line of a parabolic gencratrix to form a driving-surface,consisting of a helicoidal parabolic surface of revolution, and socombined with the propeller-shaft that a plane passed through the axisof the shaft will intersect the driving-surface of each blade in aparabola, substantially as described.

JOHN E. T. BARTLETT.

Vitnesses:

G. A. BRoUDn, SIMON VIVIAN.

